MBE growth and thermoelectric properties of Bi_2Te_3 thin films

摘要

we have grown thigh quality Bi-2Te_3 thin films on CdTe(111)B substrates using MBE. Structural poperties have been investigated using in-situ reflection high-energy electron diffraction (RHEED) and theta 2 theta X-ray diffraction analysis. They show that Bi_2Te_3 films on CdTe(111) grow along the (00.l( in the hexagonal cell with a layer-by-layer growth mode, resulting in a smooth surface, and an X-ray Bragg peak FWHM of 0.2 deg . The thermopower and electrical conductivity of the stoichiometric Bi_2Te_3 films were approx 200 mu V/K and 10~e ( OMEGA cm)~(-1), respectively, comparable to the single crystal bulk values. We have observed the antisite defect effect in Te-rich Bi_2Te_3 films: excess Te occupies Bi lattice sites and behaves as an n-type dopant. Crystallinity and transport properties are strongly affected by non-stoichiometry.